1. Field of the Invention
This invention relates to writing implements and in particular relates to non-retractable writing implements of the types commonly called ball-point pens and fiber tip pens employing a non-retractable ink cartridge resiliently mounted inside a housing having improved venting passages for permitting free communication of air and pressure equalization with the interior of the housing.
2. Description of the Prior Art
In all conventional writing implements of the types commonly referred to as ball-point pens and fiber tip pens, the pens comprise ink supply reservoirs or cartridges containing writing fluid. Ball-point pens use a viscous writing fluid and have a rotatable ball tip at the lower end of the cartridge and an open upper end. Fiber tip pens have a tip made from a fiber, such as felt or nylon, and a sponge-type reservoir for absorbing and retaining a readily flowable writing fluid. The cartridge is usually housed in a barrel or housing and if the cartridge is retractable into the barrel, the pen further comprises parts to selectively retract and advance the cartridge.
Nevertheless, in all ball-point pen or fiber tip writing implements, there is a need to provide a supply of air to replace the volume of ink used in writing operations and to equalize the pressure on the ink supply with the outside environment so that the ink can readily flow. On the other hand it is desirable to regulate or limit the flow and the quantity of air admitted to the ink in the cartridge in order to avoid excess accumulation of humid air therein and in order to preclude excessive evaporation of solvent, oxidation of the ink and other undesirable effects produced by excessive access of air to the ink.
In many writing instruments, an air vent to the atmosphere is provided by an aperture in the upper end, or in the barrel or at some location between the point and the upper end. In retractable pens, the point is usually in such a loose fit with the tip of the barrel and at the upper end where the retracting mechanism protrudes from the barrel that ample air can flow.
However, in non-retractable pens in which the relative positions of the cartridge and the barrel are rigidly fixed, a tight fit is usually required betwee the tip of the barrel and the pen point to ensure sufficient lateral point rigidity and prevent early barrel tip failure. In one particular and popular form of non-retractable ball-point writing implements, the pen comprises a plastic barrel with an ink cartridge and point assembly inserted therein. A "button" or cap is provided at its upper end to finish the pen structure. In this type of writing implement, venting is obtained through an orifice in the cap or in the barrel or by permitting loose fit of the point assembly in the barrel tip. In some of these type pens, venting is accomplished at the tip of the barrel by using a crimped metal filler tube which provides the necessary venting channels. Unfortunately, from both a cost and a production standpoint, non-metallic cartridges or easily obtainable non-crimped metal cartridges are more desirable.
Another type of non-retractable ball-point pen which vents at the tip of the barrel is disclosed in the patent to Roy M. Jenkins, U.S. Pat. No. 3,335,706. The pen disclosed in this patent has a plastic ink filled cartridge with integrally formed longitudinal venting grooves therein. However, as disclosed in the Jenkins patent, the size and depth of the grooves is critical and the proper production of the grooves requires expensive manufacturing techniques and equipment. Other venting techniques are disclosed in patents for "piggy-back" cartridges such as Gordo et al, U.S. Pat. No. 2,910,045; Seyer, U.S. Pat. No. 2,971,494 and Malm et al, U.S. Pat. No. 3,282,254. Obviously, the piggy-back cartridges only solve the problem of venting the lower cartridge past the point of the upper cartridge and do not teach a solution to the problem of economically providing accurate venting of the pen barrel to the outside atmosphere.
It is finally noted that it might appear to be relatively simple to provide venting of the pen through an orifice in the barrel. However, this procedure requires an additional manufacturing step beyond that of molding the barrel. Furthermore, it may be aesthetically more pleasing to have a barrel that has no openings along the length thereof.